Medical image processing apparatus and medical image processing method

ABSTRACT

A medical image processing apparatus includes, an unit ( 12 ) extracting a blood vessel wall region from the image in a range including an aneurysm in an object, an unit ( 13 ) calculating the blood vessel diameter change rates of the neck portions of the aneurysm, blood vessel curvature, and blood vessel flattening ratio at each of discrete points on a blood vessel region based on the extracted blood vessel region, an unit ( 14 ) extracting, from discrete points, feature points at each of which at least one of a blood vessel diameter change rate, blood vessel curvature, and blood vessel flattening ratio exceeds a corresponding one of thresholds and decide a range for the indwelling of a stent graft in accordance with the extracted feature points, and a display unit ( 19 ) superimposing and display unrecommended ranges on a stored image.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of PCT Application No.PCT/JP2013/055701, filed Mar. 1, 2013 and based upon and claiming thebenefit of priority from Japanese Patent Application No. 2012-046397,filed Mar. 2, 2012, the entire contents of all of which are incorporatedherein by reference.

FIELD

Embodiments described herein relate generally to a medical imageprocessing apparatus and a medical image processing method.

BACKGROUND

Stent grafting is a medical treatment for preventing the rupture of anaortic aneurysm by indwelling an artificial blood vessel (graft)embedded with a mesh metal tube (stent) in the aortic aneurysm andblocking the inflow of blood into the aneurysm. In general, whenexecuting a treatment plan, an operator performs image examination firstby using an X-ray computed tomography apparatus (CT), and then selects astent graft suitable for the blood vessel shape from the resultantimage. The operator then indwells the stent graft under X-rayfluoroscopy.

A challenge of stent grafting is to suppress endoleak which sometimesoccurs after the indwelling of a stent graft. Endoleak is a phenomenonin which blood leaks from the gap between an end portion of a stentgraft and the inner wall of a blood vessel. In order to eliminate such agap, it is required to carefully decide stent graft indwellingpositions.

CITATION LIST Patent Literature

Patent Literature 1: Jpn. Pat. Appin. KOKAI Publication No. 2010-088795

It is an object to provide information for supporting the decision ofstent graft indwelling positions.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the arrangement of an X-rayangiographic diagnostic apparatus including a stent graft indwellingsupport apparatus according to an embodiment.

FIG. 2 is a flowchart showing a procedure for decision supportprocessing for stent graft indwelling planned positions by the stentgraft indwelling support apparatus in FIG. 1.

FIG. 3 is a flowchart showing a procedure for stent graft decisionsupport processing by the stent graft indwelling support apparatus inFIG. 1.

FIG. 4 is a flowchart showing an endoleak check support procedure by thestent graft indwelling support apparatus in FIG. 1.

FIG. 5 is a view corresponding to step S101 in FIG. 2.

FIG. 6 is a view corresponding to step S102 in FIG. 2.

FIG. 7 is a view corresponding to step S103 in FIG. 2.

FIG. 8 is a view showing discrete points corresponding to step S104 inFIG. 2.

FIG. 9 is a view corresponding to step S104 in FIG. 2.

FIG. 10 is a view corresponding to steps S105 to S108 in FIG. 2.

FIG. 11 is a view corresponding to step S109 in FIG. 2.

FIG. 12 is a view corresponding to step S109 in FIG. 2.

FIG. 13 is a view corresponding to step S301 in FIG. 4.

FIG. 14 is a view showing a CT section passing through the positionspecified in step S301 in FIG. 4.

FIG. 15 is a view showing the imaging angle optimal for a visual checkof endoleak in step S302 in FIG. 4.

FIG. 16 is a view showing a method of deciding an imaging angle optimalfor a visual check of endoleak in step S302 in FIG. 4.

FIG. 17 is a view showing a method of deciding an imaging angle optimalfor a visual check of endoleak in step S302 in FIG. 4.

FIG. 18 is a view showing the neck portions of an aneurysm.

FIG. 19 is a view showing a stent graft indwelled in the neck portionsof an aneurysm.

DETAILED DESCRIPTION

A medical image processing apparatus according to this embodiment willbe described below with reference to the accompanying drawings. Themedical image processing apparatus according to the embodiment includesan image storage unit which stores the data of a processing targetimage. The processing target image includes the aneurysm in an objectand a blood vessel portion in which the aneurysm is formed. Thisapparatus extracts a blood vessel wall region from the image. Theapparatus calculates a blood vessel diameter change rate, blood vesselcurvature, and blood vessel flattening ratio at each of a plurality ofdiscrete points on the blood vessel wall region from the extracted bloodvessel wall region. The apparatus extracts feature points, from theplurality of discrete points, at each of which at least one of the bloodvessel diameter change rate, blood vessel curvature, and blood vesselflattening ratio exceeds a corresponding one of thresholds. Theapparatus decides a range for the indwelling of a stent graft for theaneurysm in accordance with the extracted feature points. Each decidedrange is superimposed and displayed on an image.

The terms used will be defined first as follows.

As shown in FIG. 18, neck portions are healthy blood vessel portions, ofa blood vessel with an aneurysm, which lead to the aneurysm from its twosides. In practice, the neck portions are blood vessel portions in anROI (to be described later) and located in ranges excluding the aneurysmregion. As shown in FIG. 19, it is possible to properly suppressendoleak by bringing the outer circumferential portions of the two endsof a stent graft into tight contact with the inner walls of the neckportions. This suppression can suppress a local abnormal dilation of ablood vessel, i.e., an aneurysm.

Unrecommended regions are blood vessel portions, of neck portions, whichare not suitable for the indwelling of a stent graft, i.e., blood vesselportions with high possibility of endoleak. Note that this embodimenthas a feature that it technically defines blood vessel portionsunsuitable for the indwelling of a stent graft, automatically identifiessuch unrecommended regions in accordance with the definition, andpresents the unrecommended regions to an operator (doctor) to supportmaking a treatment plan.

Recommended regions are blood vessel portions suitable for theindwelling of a stent graft, i.e., blood vessel portions with lowpossibility of endoleak. For example, recommended regions are bloodvessel portions obtained by excluding unrecommended regions from neckportions. Such regions will be described in detail later.

Endoleak is a phenomenon that gaps are formed between the outercircumferential portions of the two ends of a stent graft and the innerwall portions of a blood vessel at neck portions after the indwelling ofthe stent graft to make blood leak from the gaps, thereby causingsuppressed blood to flow into the aneurysm. Gaps are formed mainly dueto insufficient contact between the outer circumferential portions ofthe two ends of a stent graft and the inner wall portions of a bloodvessel at neck portions.

An ROI (Region of Interest) is originally a region of user's interest.In this case, an ROI is particularly a local range which forms an innerportion of an image set by the user as a processing target range for theidentification of unrecommended regions and recommended regions.

FIG. 1 is a block diagram showing the arrangement of an X-rayangiographic diagnostic apparatus including a stent graft indwellingsupport apparatus according to this embodiment. An X-ray tube 3generates X-rays upon receiving a high voltage (tube voltage) and afilament current from a high voltage generator 5. An X-ray stop unit 4for forming X-rays in an arbitrary shape is attached to the X-rayemission window of the X-ray tube 3. The X-ray tube 3 is attached to oneend of an arm 1 in the shape of, for example, C. An X-ray flat paneldetector 6 facing the X-ray tube 3 is attached to the other end of theC-arm 1. The X-ray flat panel detector 6 is a so-called flat paneldetector, which has a plurality of detection elements arrayedtwo-dimensionally to directly or indirectly convert incident X-rays intoelectric charge. An output from the X-ray flat panel detector 6 issupplied as X-ray image data to a stent graft indwelling supportapparatus 9 via an image memory 7. An object P placed on a bed (notshown) is disposed between the X-ray tube 3 and the X-ray flat paneldetector 6. A support mechanism (not shown) supports the C-arm 1 so asto allow it to independently rotate about three orthogonal axes. Amechanism control unit 2 controls the support mechanism of the C-arm 1to arbitrarily change an imaging angle (working angle) relative to theobject P. When performing imaging, a system control unit 8 controls themechanism control unit 2, the high voltage generator 5, the X-ray flatpanel detector 6, and the image memory 7.

The stent graft indwelling support apparatus 9 includes a stent graftindwelling support control unit 10 as a main unit and an image storageunit 11. The image storage unit 11 stores image data in a rangeincluding the aneurysm, which is generated by a medical image generationapparatus such as an X-ray computed tomography apparatus (CT) for theobject. This image data is typically a tomographic image, which will bedescribed as a CT image. The operator sets, as a processing target, alocal range (a region of interest ROI in this case) including ananeurysm on a CT image via an operation unit 18.

A blood vessel extraction unit 12 extracts a blood vessel wall region byarbitrary processing such as threshold processing upon localization tothe region of interest ROI of the tomographic image, and also specifiesa blood vessel centerline from the extracted blood vessel wall region. Ablood vessel centerline is specified as a string of points equidistantfrom, typically, the inner blood vessel wall on one side and the innerblood vessel wall on the opposite other side on the tomographic image.The blood vessel extraction unit 12 extracts a plaque portion and acalcified portion by localization to the region of interest ROI on thetomographic image by threshold processing using thresholds unique to theplaque portion and the calcified portion.

A blood vessel form index calculation unit 13 calculates indices (bloodvessel form indices) representing a blood vessel form concerning theneck portions of the aneurysm based on the extracted blood vessel regionand blood vessel centerline. The blood vessel form index calculationunit 13 calculates, as blood vessel form indices, a blood vesseldiameter change rate, blood vessel curvature, and blood vesselflattening ratio at each of a plurality of discrete points which arelocated on the blood vessel centerline and arranged at equal intervals.A blood vessel diameter is the distance between the intersections of aline orthogonal to a blood vessel centerline at each discrete point andthe inner wall portions of a blood vessel wall region on the two sides.A blood vessel diameter change rate is calculated as the value obtainedby normalizing the difference between the maximum blood vessel diameterand the minimum blood vessel diameter in a predetermined range centeredon each point on the blood vessel centerline with the blood vesseldiameter at the corresponding point. A blood vessel curvature is thecurvature of a blood vessel centerline at each of a plurality of pointson a blood vessel centerline. A blood vessel flattening ratio is theratio of the minimum blood vessel diameter to the maximum blood vesseldiameter on a blood vessel cross-section orthogonal to a blood vesselcenterline at each of the plurality of points on the blood vesselcenterline. Note that an MPR processing unit (not shown) may generate atomographic image of a blood vessel cross-section from volume data in arange including the aneurysm by MPR (Multi Planar Reconstruction).Alternatively, the tomographic image data of a blood vesselcross-section may be received from an external system 20.

A recommended/unrecommended region decision unit 14 extracts, from aplurality of discrete points on a blood vessel centerline, points atwhich the blood vessel diameter change rates exceed the first threshold.The recommended/unrecommended region decision unit 14 extracts, from theplurality of discrete points on the blood vessel centerline, points atwhich the blood vessel curvatures exceed the second threshold. Therecommended/unrecommended region decision unit 14 also extracts, fromthe plurality of discrete points on the blood vessel centerline, pointsat which the blood vessel flattening ratios exceed the third threshold.In addition, the recommended/unrecommended region decision unit 14extracts, as a plurality of unrecommended points (feature points), aplurality of points at each of which at least one of the blood vesseldiameter change rate, blood vessel curvature, and blood vesselflattening ratio exceeds a corresponding one of thresholds. Furthermore,the recommended/unrecommended region decision unit 14 extracts, asunrecommended points, points included in circles each having, as itsradius, a predetermined distance from an end portion of each of theextracted plaque and calcified portions.

The recommended/unrecommended region decision unit 14 decides anunrecommended region from a range in which a plurality of extractedunrecommended points constitute strings. Note that therecommended/unrecommended region decision unit 14 may decide a singleunrecommended region or a plurality of discrete unrecommended regions.

The recommended/unrecommended region decision unit 14 decidesrecommended regions. The recommended regions are those obtained byexcluding the unrecommended regions from the neck portions. Therecommended/unrecommended region decision unit 14 decides, as arecommended region, a region having both a blood vessel diameter changerate and a curvature which are less than the corresponding thresholds orother lower thresholds and a length exceeding the necessary length of anend portion of the stent graft.

A display unit 19 superimposes and displays translucent area marksrespectively indicating the recommended regions and the unrecommendedregions on a tomographic image of a blood vessel cross-section under thecontrol of the stent graft indwelling support control unit 10. An areamark indicating an unrecommended region has a display form, e.g., acolor, different from that of an area mark indicating a recommendedregion. The operator designates stent graft indwelling planned positionsin the respective recommended regions of the neck portions on the twosides of the aneurysm while checking the recommended regions and theunrecommended regions on the image. In this case, the stent graftindwelling planned positions are the positions of one end portion andthe other end portion of the stent graft.

A stent graft specification decision unit 16 decides specificationsconcerning a stent graft required for this aneurysm treatment based onthe stent graft indwelling planned positions and the blood vessel formindices. In general, the specifications of a stent graft are often givenby an aneurysm size, neck diameters, and maximum curvature. The stentgraft specification decision unit 16 decides an “aneurysm size” from thedistance between the indwelling planned positions on the two sides. Thestent graft specification decision unit 16 decides “neck diameters” fromblood vessel diameters at the indwelling planned positions on the twosides. The stent graft specification decision unit 16 decides themaximum value of the blood vessel curvatures between the indwellingplanned positions on the two sides as a “maximum curvature”.

The stent graft specification decision unit 16 searches an informationdatabase concerning many stent graft products, which is stored inadvance in a device management information storage unit 15, according tothe decided stent graft specifications, and extracts at least one stentgraft product having specifications matching the stent graftspecifications.

An endoleak imaging angle decision unit 17 decides, at the stent graftindwelling planned positions, a position, in the contact ranges betweenthe two ends of the stent graft and the blood vessel wall, at which thepossibility of the occurrence of endoleak is highest, and an imagingangle which most facilitates visual recognition of the occurrence ofendoleak at the decided position. More specifically, the endoleakimaging angle decision unit 17 specifies a point, in the contact rangesbetween the two ends of the stent graft and the blood vessel wall, atwhich the blood vessel flattening ratio is highest. The endoleak imagingangle decision unit 17 decides this point as the center of an imagingfield of view. The endoleak imaging angle decision unit 17 also decides,as an imaging angle, a direction orthogonal to a plane determined by thelongest diameter passing through the point at which the blood vesselflattening ratio is highest and a blood vessel centerline segmentintersecting the diameter at the point and located near the point.

The display unit 19 superimposes and displays area marks indicatingunrecommended regions and recommended regions on the CT image datastored in the image storage unit 11 or the live image generated by theX-ray angiographic diagnostic apparatus incorporated in the stent graftindwelling support apparatus 9. A concrete example of the display formof area marks will be described later. At the stage of planning a stentgraft indwelling planned treatment, the doctor can decide stent graftindwelling planned positions by visually checking unrecommended regionsand recommended regions and the forms of an aneurysm and blood vesselportions near it on a CT image. In addition, at the stage of operatingduring a stent graft indwelling treatment, the doctor can execute theoperation of indwelling the stent graft while visually checking theunrecommended regions and recommended regions on a live image.

The stent graft indwelling support apparatus 9 may generate stent graftindwelling support information from a medical imaging apparatus otherthan the X-ray angiographic diagnostic apparatus incorporated in thestent graft indwelling support apparatus 9 or from past image dataconcerning the object which is stored in an external system. With regardto past image data, the stent graft indwelling support apparatus 9 maygenerate stent graft indwelling support information from, for example,the image data which can be supplied from a hospital information system22 of the external system 20 via a LAN network 21 in the hospital orfrom the image data supplied from a recording medium 23 such as a memorycard via an image data transfer unit 24. Images to be used may be X-rayimages, CT images, MRI images, and images generated by other modalities.

The device management information storage unit 15 stores devicemanagement information concerning various types of stent graft productswhich is supplied via the Internet or the recording medium 23. Devicemanagement information includes information concerning specificationssuch as the model numbers, shapes, and sizes of various stent graftproducts (called devices) provided from a plurality of stent graftproviders. The stent graft specification decision unit 16 decidesspecifications concerning the thickness, curvature, and length requiredfor a stent graft in accordance with the blood vessel diameters at thetwo end portions of the stent graft at indwelling planned positions, themaximum curvature of the two end portions, and the length between thetwo end portions, which are set in accordance with operator instructionsinput via the operation unit 18, and extracts device managementinformation from devices (stent graft products) satisfying thespecifications. The display unit 19 displays a list of such products.

FIG. 2 shows a procedure for decision support processing for stent graftindwelling planned positions in this embodiment. The final object ofthis support processing is to superimpose and display area marksindicating recommended regions recommended as stent graft indwellingpositions and area marks indicating unrecommended regions unrecommendedas stent graft indwelling positions on a tomographic image, and providedevice information of a stent graft product corresponding to stent graftindwelling planned positions. This processing provides an imaging anglesuitable for a check on the occurrence of endoleak after operation.

As shown in FIG. 5, the operator operates the operation unit 18 to set aregion of interest ROI on a portion of a CT image of a longitudinalsection of the target blood vessel displayed on the display unit 19(step S101). A decision support processing target for stent graftindwelling planned positions is limited to the region of interest ROI.In step S102, the blood vessel extraction unit 12 extracts a bloodvessel region by localization to the region of interest ROI of thetomographic image by threshold processing, as shown in FIG. 6. The bloodvessel extraction unit 12 specifies a blood vessel centerline as astring of points equidistant from opposite blood vessel wall regions.The blood vessel extraction unit 12 extracts a plaque portion and acalcified portion by threshold processing using thresholds unique to theplaque portion and the calcified portion upon localization to the regionof interest ROI of the tomographic image. In step S103, the blood vesselextraction unit 12 specifies an aneurysm region by, for example, patternrecognition for an extracted blood vessel wall region (FIG. 7).

As shown in FIG. 8, based on an extracted blood vessel wall region andblood vessel centerline, the blood vessel form index calculation unit 13calculates a blood vessel diameter change rate, blood vessel curvature,and blood vessel flattening ratio at each of multiple discrete points ona blood vessel wall region other than the aneurysm region or the bloodvessel centerline (step S105). As described above, the blood vessel formindex calculation unit 13 calculates, as a blood vessel diameter, thedistance between the intersections of a line orthogonal to a bloodvessel centerline at each discrete point and the inner wall portions ofa blood vessel wall region on the two sides. The blood vessel form indexcalculation unit 13 calculates, as a blood vessel diameter change rate,the value obtained by normalizing the difference between the maximumblood vessel diameter and the minimum blood vessel diameter in apredetermined range centered on each point on a blood vessel centerlinewith the blood vessel diameter at the point. The blood vessel form indexcalculation unit 13 calculates, as a blood vessel curvature, thecurvature of a blood vessel centerline at each of a plurality of pointson the blood vessel centerline. The blood vessel form index calculationunit 13 calculates, as a blood vessel flattening ratio, the ratio of theminimum blood vessel diameter to the maximum blood vessel diameter on ablood vessel cross-section orthogonal to a blood vessel centerline ateach of a plurality of points on the blood vessel centerline.

The recommended/unrecommended region decision unit 14 decides regions(recommended regions) recommended as stent graft indwelling positionsand regions (unrecommended regions) which are not recommended, based onthese calculated blood vessel form indices (step S106). Morespecifically, as shown in FIG. 9, the recommended/unrecommended regiondecision unit 14 extracts, as unrecommended points, points, from aplurality of discrete points on a blood vessel centerline, at each ofwhich at least one of the blood vessel diameter change rate, bloodvessel curvature, and blood vessel flattening ratio exceeds acorresponding one of thresholds determined for the respective values. Inaddition, the recommended/unrecommended region decision unit 14extracts, as unrecommended points, points included in circles eachhaving, as its radius, a predetermined distance from an end portion ofeach of the extracted plaque and calcified portions. Note that theoperator can arbitrarily change the thresholds respectively determinedfor blood vessel diameter change rates, blood vessel curvatures, andblood vessel flattening ratios (step S107).

The recommended/unrecommended region decision unit 14 decides one or twoor more unrecommended regions in accordance with the point string rangeof the extracted unrecommended points (step S108). Therecommended/unrecommended region decision unit 14 also decides, as arecommended region, a region which is obtained by excluding anunrecommended region from a neck portion. This region corresponds to apoint string range of discrete points in which both a blood vesseldiameter change rate and a curvature are less than the correspondingthresholds or other lower thresholds. The region also has a lengthexceeding the necessary length of an end portion of the stent graft(step S109).

As shown in FIGS. 10, 11, and 12, the display unit 19 superimposes anddisplays translucent area marks indicating the unrecommended regions ona tomographic image of a blood vessel cross-section under the control ofthe stent graft indwelling support control unit 10 (step S110). Thedisplay unit 19 displays area marks indicating recommended regionstogether with the area marks indicating the unrecommended regions, asneeded. In this case, the display unit 19 displays the area marksindicating the unrecommended regions in a display form, typically, acolor, different from that of the area marks indicating the recommendedregions. The operator operates the operation unit 18 to designate stentgraft indwelling planned positions in the respective recommended regionsof the neck portions on the two sides of the aneurysm while checking therecommended regions and the unrecommended regions on the image (stepS111). In practice, when the doctor performs stent graft indwellingtreatment under X-ray fluoroscopy, area marks indicating unrecommendedregions are superimposed on a real-time fluoroscopic image. Area marksindicating recommended regions are also superimposed on the real-timefluoroscopic image, as needed (step S112).

FIG. 3 shows stent graft specification decision processing by the stentgraft specification decision unit 16. The stent graft specificationdecision unit 16 decides specifications concerning a stent graftrequired for the aneurysm treatment based on the stent graft indwellingplanned positions and the blood vessel form indices (step S201). Thedecided specifications include an aneurysm size, neck diameters, andmaximum curvature. The stent graft specification decision unit 16decides an “aneurysm size” from the distance between the indwellingplanned positions on the two sides or the diameter of the aneurysmregion specified by pattern recognition. The stent graft specificationdecision unit 16 decides “neck diameters” from blood vessel diameters,average diameters, or maximum diameters at the indwelling plannedpositions on the two ends of the stent graft. The stent graftspecification decision unit 16 decides the maximum value of blood vesselcurvatures between the indwelling planned positions of the stent graftas a “maximum curvature”.

The stent graft specification decision unit 16 searches an informationdatabase concerning many stent graft products stored in advance in thedevice management information storage unit 15 based on the decided stentgraft specifications. This decides at least one stent graft productsatisfying the decided stent graft specifications. The display unit 19displays a list of decided stent graft products (step S202). Forexample, the display unit 19 displays maker names, correspondinganeurysm sizes, neck diameters, and maximum curvatures as stent graftproduct information.

It is necessary to perform follow-up observation after the completion ofstent graft indwelling. It is most important in this follow-upobservation to check the occurrence of endoleak. The endoleak imagingangle decision unit 17 decides an imaging angle exemplified in FIG. 15which is most suitable for a check on the occurrence of endoleak. Theendoleak imaging angle decision unit 17 may execute this decision,together with indwelling support, at the stage of indwelling supportbefore stent graft indwelling or may execute the decision before a checkon the occurrence of endoleak. The latter will be described below.

According to the above description, recommended regions andunrecommended regions are two-dimensional ranges. However, they may beone-dimensional ranges which can be expressed by points and lines orthree-dimensional ranges which can be expressed stereoscopically. Whenexpressing recommended regions and unrecommended regions asthree-dimensional ranges, this apparatus stereoscopically displays therecommended regions and the unrecommended regions together with athree-dimensional CT image by volume rendering processing like thatshown in, for example, FIG. 13 or 15. When rotating and displaying athree-dimensional CT image, the apparatus rotates and displaysrecommended regions and unrecommended regions together with thethree-dimensional CT image. This allows to three-dimensionally recognizethe recommended regions and unrecommended regions together with theaneurysm and the blood vessel.

As shown in FIG. 14, the possibility of endoleak is highest at a portionbetween the stent graft and the blood vessel wall where the gap(hatching) is largest. As shown in FIG. 4, first of all, in step S301,the apparatus specifies, from the latest CT image, a position, in anintra-neck range in which the two ends of the stent graft are in contactwith the blood vessel wall, at which the blood vessel flattening ratiois highest, at each stent graft indwelling position (FIG. 13). In stepS302, as shown in FIGS. 16 and 17, the apparatus decides, as an imagingangle, a direction orthogonal to a plane determined by the longestdiameter passing through the point at which the blood vessel flatteningratio is highest and a blood vessel centerline segment intersecting thepoint and located near the point.

The apparatus moves the C-arm in accordance with the decided imagingangle under the control of the system control unit 8 (step S303). Theapparatus executes contrast radiography at this imaging angle (stepS304).

As has been described above, according to this embodiment, it ispossible to expect a reduction in endoleak occurrence rate, a reductionin burden on the user, shortening of operation time, a reduction inexposure dose, and a reduction in the amount of contrast medium used.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A medical image processing apparatus comprising:an image storage memory configured to store data of an image includingan aneurysm in an object; processing circuitry configured to extract ablood vessel wall region from the image; calculate a blood vesseldiameter change rate, a blood vessel curvature, and a blood vesselflattening ratio at each of a plurality of discrete points on the bloodvessel wall region based on the extracted blood vessel wall region;extract a plurality of feature points from the plurality of discretepoints based on at least one of the blood vessel diameter change rate,the blood vessel curvature, and the blood vessel flattening ratio; anddecide a range for indwelling of a stent graft for the aneurysm inaccordance with the extracted feature points; and a display configuredto superimpose and display the range on the stored image.
 2. The medicalimage processing apparatus of claim 1, wherein the range comprises arange displayed two-dimensionally or three-dimensionally.
 3. The medicalimage processing apparatus of claim 2, wherein the processing circuitryextracts, as the feature points from the plurality of discrete points, aplurality of unrecommended points at each of which at least one of theblood vessel diameter change rate, the blood vessel curvature, and theblood vessel flattening ratio exceeds a corresponding one of thresholds,and the processing circuitry decides an unrecommended range which is notrecommended for indwelling of a stent graft for the aneurysm inaccordance with the extracted unrecommended points.
 4. The medical imageprocessing apparatus of claim of 3, wherein the processing circuitrydecides a recommended range which is located outside the unrecommendedrange and recommended for indwelling of a stent graft for the aneurysmin accordance with a plurality of discrete points at each of which theblood vessel diameter change rate is less than a threshold correspondingto the blood vessel diameter change rate or another threshold lower thanthe threshold.
 5. The medical image processing apparatus of claim 3,wherein the processing circuitry decides a recommended range which islocated outside the unrecommended range and recommended for indwellingof a stent graft for the aneurysm in accordance with a plurality ofdiscrete points at each of which the blood vessel curvature is less thana threshold corresponding to the blood vessel curvature or anotherthreshold lower than the threshold.
 6. The medical image processingapparatus of claim 3, wherein the processing circuitry decides a bloodvessel neck portion which is located outside the unrecommended range andhas a length exceeding a necessary length of an end portion of the stentgraft as a recommended range recommended for indwelling of a stent graftfor the aneurysm.
 7. The medical image processing apparatus of claim 4,wherein the decided recommended range is displayed, together with theunrecommended range, while being superimposed on the image.
 8. Themedical image processing apparatus of claim 5, wherein the displaysuperimposes and displays at least one of the unrecommended range andthe recommended range on a live image generated by an external X-rayangiographic diagnostic apparatus.
 9. A medical image processingapparatus comprising: an image storage memory configured to store dataof an image including an aneurysm in an object; processing circuitryconfigured to extract a blood vessel wall region from the image;calculate a blood vessel diameter change rate, a blood vessel curvature,and a blood vessel flattening ratio at each of a plurality of discretepoints on the blood vessel wall region based on the extracted bloodvessel wall region; extract, from the plurality of discrete points, anunrecommended point at which at least one of the blood vessel diameterchange rate, the blood vessel curvature, and the blood vessel flatteningratio exceeds a corresponding one of thresholds; and decide anunrecommended range which is not recommended for indwelling of a stentgraft for the aneurysm in accordance with a point string range of theextracted unrecommended points; and a display configured to superimposeand display the unrecommended range on the stored image.
 10. The medicalimage processing apparatus of claim 9, wherein the processing circuitrysets a local range including the aneurysm in the image as a region ofinterest, and the processing circuitry localizes a processing range tothe region of interest.
 11. The medical image processing apparatus ofclaim 9, wherein the processing circuitry decides a range which islocated outside the unrecommended range and in which both the bloodvessel diameter change rate and the blood vessel curvature each arelower than a corresponding one of the thresholds or another thresholdlower than the threshold as a recommended range recommended forindwelling of a stent graft for the aneurysm.
 12. The medical imageprocessing apparatus of claim 11, wherein the processing circuitryexcludes a plaque portion or a calcified portion identified from theimage from the recommended range.
 13. The medical image processingapparatus of claim 11, wherein the decided recommended range isdisplayed, together with the unrecommended range, while beingsuperimposed on the image.
 14. The medical image processing apparatus ofclaim 9, wherein the display superimposes and displays at least one ofthe unrecommended range and the recommended range on a live imagegenerated by an external X-ray angiographic diagnostic apparatus. 15.The medical image processing apparatus of claim 9, wherein theprocessing circuitry changes the threshold in accordance with anoperator instruction.
 16. The medical image processing apparatus ofclaim 9, wherein the processing circuitry decides specificationsconcerning a thickness, a curvature, and a length required for the stentgraft in accordance with blood vessel diameters of two end portions ofthe stent graft at indwelling planned positions, a maximum curvature ofthe two end portions, and a length between the two end portions whichare set on the image in accordance with an operator instruction.
 17. Themedical image processing apparatus of claim 16, wherein the processingcircuitry specifies a stent graft product or a stent graft type suitablefor the specifications from stent graft production managementinformation.
 18. The medical image processing apparatus of claim 9,wherein the processing circuitry specifies a position indicating amaximum blood vessel flattening ratio at two end portions of the stentgraft which are located at indwelling planned positions so as tosuperimpose and display the position as a position on the image at whicha possibility of occurrence of endoleak is high.
 19. The medical imageprocessing apparatus of claim 18, wherein the processing circuitrydecides an imaging angle orthogonal to a blood vessel long axis at aposition indicating the maximum blood vessel flattening ratio and ablood vessel centerline.
 20. A medical image processing methodcomprising: extracting a blood vessel wall region from an imageincluding an aneurysm in an object; calculating a blood vessel diameterchange rate, a blood vessel curvature, and a blood vessel flatteningratio at each of a plurality of discrete points on the blood vessel wallregion based on the extracted blood vessel wall region; extracting, fromthe plurality of discrete points, an unrecommended point at which atleast one of the blood vessel diameter change rate, the blood vesselcurvature, and the blood vessel flattening ratio exceeds a correspondingone of thresholds; deciding an unrecommended range which is notrecommended for indwelling of a stent graft for the aneurysm inaccordance with a point string range of the extracted unrecommendedpoints; and superimposing and displaying the unrecommended range on thestored image.
 21. The medical image processing method of claim 20,wherein a range which is located outside the unrecommended range and inwhich both the blood vessel diameter change rate and the blood vesselcurvature each are lower than a corresponding one of the thresholds oranother threshold lower than the threshold is decided as a recommendedrange recommended for indwelling of a stent graft for the aneurysm. 22.The medical image processing method of claim 21, wherein the decidedrecommended range is displayed, together with the unrecommended range,while being superimposed on the image.